rate = ratio = quotient

Dear BeBeMala,

a person drove 310 kilometers in 4 hours. at this rate,how far will the person travel in 10 hours?

You can creat a ratio: 310km/4h = 77.5 km/h. This is the rate in "at this rate". That we can call quotient or motient rate or velocity or simply speed.
This ratio says we drive 77.5km during 1 hours. How many kilometers can we drive in 10 hours? Of course 10*77.5 = 775 km.

One more:
1) step: find out the rate (rate = 77.5 km/h)
2) step: use the rate in a new time (s = rate*time = 77.5 km/h * 10 h)

a carton contains 946 milliliters of milk.how many liters of milk are contained in 10 cartons?